1. Field of the Invention
The present invention relates to torque proportioning differential drives.
2. Description of the Prior Art
In 1958, U.S. Pat. No. 2,859,641, issued to V. E. Gleasman on a Differential Gear Mechanism, and disclosed a differential utilizing worms and worm gears arranged around a central hub and driven from a ring gear. This differential concept was refined in various ways by Gleasman, and in the February 1984 issued of Popular Science, pages 58 through 61, an article entitled "The Strange Geometry of Gleason's Impossible Differential", was published explaining the principles advanced by Gleasman. The discussion in Popular Science points up the differences between the differential using the principles set forth in the Gleasman patent, and the conventional bevel gear differential. The terminology in the Popular Science article uses the term "worm gear" for the "worm" and the term "worm wheel" for the worm gear, so the terminology used herein is slightly different.
However, Gleasman uses "worm gears" as axle side gears and three paris of "worm wheels" with integral spur balancing gears which function to prevent rotation of worm wheels during drive, to transmit and balance opposite rotation of worm wheels as they are rotated by axle worms during differentiation, and to transmit the torque thrust from the driven gear carrier via the worm wheel on the good traction side to the worm wheel on the poor traction side which worm wheel cannot rotate the axle worm gear thus proportioning torque to the good traction side. The Gleasman drive is based on the principle that a worm gear (or worm wheel as Gleasman calls it) cannot drive a worm, but the worm can drive the worm gear or worm wheel. Gleasman teaches that lead angles of the worm should be between 27 and 35 degrees, which provide anti reverse features and minimize adverse effects of shear forces.
Another differential mechanism using the principles of worm and worm gear drives is shown in U.S. Pat. No. 2,666,343, issued to Casa-Massa. The arrangement in this patent is different than that shown in the Gleasman patent.
Patents disclosing various forms of this concept have issued to Gleasman in the ensuing years, but none of the differentials utilizing the worm-worm gear irreversible drive feature has the power divided between two power paths comprising, as shown, parallel shafts that are each coupled to a worm mounted onto a separate control bevel gear of separate bevel gear differentiating gear clusters through which the respective outputs shafts are driven.
In the present invention, the worms are coupled together through a single worm gear (which is drivably engaged with both worms) to provide especially the means (irreversible drive feature) for proportioning torque to the good traction side of a vehicle while, at the same time, controlling the rotation of worms and attached control bevel gears which operate through separate bevel gear differentiating gear clusters, allowing the worms and attached control bevel gears to rotate in opposite directions to the extent that rpm differentiation is required, while regulating the rotation of the control bevel gears to allow continuous proportioned driving torque to be transmitted via orbiting spider gears to the separate power shafts, whether or not differentiation is occuring. Proper differentiation is caused to occur even with poor traction on one side of the vehicle, as does Gleasman's differential. With good traction on both sides of the vehicle, the conventional differential will also properly differentiate, that is, in turn one axle will rotate faster, and the other axle rotate slower, by the same number of rpm, than the rpm of the driven gear carrier.
The differentiating gear clusters in the present device are both driven from one input shaft and drive the output shafts from the differential to in turn drive rear axle assemblies.